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980512a5ca
Add initial dts for CanMV-K230 and K230-EVB powered by Canaan Kendryte
K230 SoC [1].
Some key consideration:
- Only place BigCore which is 1.6GHz RV64GCBV
The existence of cache coherence between the two cores remains unknown
since they have dedicated L2 caches. And the factory SDK uses it for
other OS by default. I don't know whether the two CPUs on K230 SoC
can be used in one system. So only place BigCore here.
Meanwhile, although docs from Canaan said 1.6GHz Core with Vector is
CPU1, the CSR.MHARTID of this core is 0.
- Support for "zba" "zbb" "zbc" "zbs" are tested by hand
The user manual of C908 from T-Head does not document it specifically.
It just said it supports B extension V1.0. [2]
I have tested it by using this [3] which attempts to execute "add.uw",
"andn", "clmulr", "bclr" and they doesn't traps on K230. But on JH7110,
"clmulr" and "bclr" will trap.
- Support for "zicbom" is tested by hand
Have tested with some out-of-tree drivers from [4] that need DMA and they
do not come to the dts currently.
- Support for "zicboz" is tested by hand
Have tested with my own bare mental M-Mode program [5] which tries to use
zicboz to clear a 64B aligned block and got output[6] shows it supports
zicboz.
- Cache parameters are inferred from T-Head docs [2] and Canaan docs [1]
L1i: 32KB, VIPT 4-Way set-associative, 64B Cacheline
L1d: 32KB, VIPT 4-Way set-associative, 64B Cacheline
L2: 256KB, PIPT 16-way set-associative, 64B Cacheline
The numbers of cache sets are calculated from these parameters.
- MMU only supports Sv39
The T-Head docs [2] say the C908 core can be configured to support Sv48 and
Sv39 or only Sv39. On K230, I tried to write "riscv,sv48" on mmu-type in
dts and boot the mainline kernel. However, it failed during the kernel
probe and fell back to Sv39. I also tested it on M-Mode software, writing
Sv48 to satp.mode will not trap but will leave the CSR unchanged. While
writing Sv39, it will take effect. It shows that this CPU does not support
Sv48.
- Svpbmt and T-Head MAEE both supported
T-Head C908 does support both Svpbmt and T-Head MAEE for page-based memory
attributes and is controlled by BIT(21) on CSR.MXSTATUS. The Svpbmt is used
here for mainline kernel support for K230. If the kernel wants to use
Svpbmt, the M-Mode software should unset BIT(21) of CSR.MXSTATUS before
entering the S-Mode kernel. Otherwise, the kernel will not boot, as 0 on
T-Head MAEE is NonCachable Memory. Once the kernel switches from bare metal
to Sv39, It will lose dirty cache line modifications that haven't been
written back to the memory.
[1] https://developer.canaan-creative.com/k230/dev/zh/00_hardware/K230_datasheet.html#chapter-1-introduction
[2] https://occ-intl-prod.oss-ap-southeast-1.aliyuncs.com/resource//1699268369347/XuanTie-C908-UserManual.pdf
[3] https://github.com/cyyself/rvb_test
[4] https://github.com/cyyself/linux/tree/k230-mainline
[5]
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